Just tested onhttps://pieregister.com/forums/topic/logout-url-not-working/?piereg_logout_url=true&redirect_to=http%3A%2F%2Fpieregister.genetechsolutions.com%2Fforums%2Ftopic%2Flogout-url-not-working%2F

It looks like its working fine for us, please make sure:
1.) You have blocked wp-login pages
2.) providing redirect_to URL value